1.
Note, however, that the second half of Physics is less
integrated than the first: it contains the apparently self-standing
treatment of the unmoved mover and of the eternity of motion in bk. 8.
(See Falcon 2016.) Note, furthermore, that Aristotle, at
Physics 8.5, 257a34f refers to a proof in bk. 6 as one from
the general discussion of nature, i.e. as to something which
featured in a different work.

Moreover, the way bk. 7 was joined to these discussions, is somewhat
problematic: Aristotle's disciple, Eudemus, when putting together his
own Physics, according to Simplicius’ testimony
(Commentary on the Physics, p. 1036f.) did not discuss the
material in bk. 7, although he followed the discussion of both
Aristotelian inquiries. Furthermore, unlike the other books, part of
bk. 7 is transmitted in two significantly different versions.

We should note nevertheless that even if only later editors joined the
two discussions into the single work known to us as the
Physics, these later editors could at the very least rely on
the example of Eudemus’ Physics.

2.De caelo contains two inquiries: the first two books discuss
the problems of nature in the celestial domain, bks. 3 and 4 contain a
discussion about the four sublunary elements.

4.Aitia and aition are distinguished by e.g.
Chrysippus: the aition is a concrete object bearing causal
responsibility, whereas the aitia is the account about the
causal role of this cause. This distinction of concrete efficacy, and
the account about this efficacy is not present in Aristotle. See the
entry
Aristotle on causality.

5.
However, this matter-form complexity can reappear within the form
itself, for further discussion see the section on Matter-involving forms
in the entry on
form vs. matter.

6.
To this extent the form is at the same time a final cause for the
potentialities which are present in order to make its emergence
possible. This can justify, then, Aristotle's description of form (in
Physics 1.9) as an object of striving and matter as the
entity which in so far as it is matter strives after form.

7.
This is no mysterious pull, though, on the part of these final
causes. Rather, final causes can be operative only in the context of
conscious, or quasi-conscious aspirations (human or animal chases
food, craftsman fashions artifact with an eye to its function as
goal), and in goal-directed natural processes.

8.
See e.g. De anima (On the Soul) 2.4,
415b8–28, where after the identification of the soul as
substance (i.e. as form), and as moving cause, the passage specifies a
meaning in which the soul is also a final cause as beneficiary
(hôi) of the processes in the living being. The
converse of the assertion that natures are goals as beneficiaries is
also often asserted by Aristotle as a first assumption of natural
science. Accordingly, nature is able to produce what is best for a
particular kind, under the constraints of the given circumstances and
the prevailing preconditions. In short, nature does everything best
(see e.g. De incessu animalium [On the Progression of
Animals] 2,704b14–18, cf. Physics 2.7,
198b8–9). Clearly, this assertion presupposes that nature
features here as a (goal-directed) efficient cause, otherwise it would
not make sense that nature does anything.

9.
This is so already at the end of the Categories, where
motion features as one of the postpraedicamenta, and the
kinds of motion—generation, perishing, growth, decay, alteration
and locomotion—are listed separately, according to the
categorical status of entities acquired (and replaced) through the
motion.

10.Physics 5.1, 225b5–9. Position and possession (items
(9) and (10) of the list of categories in the Categories) do
not feature on this list. Moreover, time is also missing in the
parellel version of the passage in Metaphysics bk. 11, in the
text as read by Simplicius, and in some manuscripts.

11.
Aristotle at some places distinguishes change
(metabolê) and motion (kinêsis) and claims
that changes in substance—generations and perishings—are
not motions. This leads then at these places to a three-element list
of motions. For the considerations leading to the exclusion of change
in substance from among the other motions see Physics
5.1–2, with the concluding doctrinal statement at 5.2,
226a23–25. Throughout this article I follow Aristotle's less
rigorous terminology, where change and motion are not distinguished.

12.
This does not mean that the inclusion of motions in the categories of
action and passion would be necessarily wrong-headed. Something at
least analogous to the categorical bifurcation of action and passion
is strongly suggested by a remark of Aristotle in the course of the
discussion whether the item effecting change and the item undergoing
change have identical or different actualities. There Aristotle says
that “it is unreasonable that two entities which are different
in kind should have the same actuality” (Physics 3.3,
202a36–b2). (Note, however, that this consideration will be
mitigated by the claim at 202b19–21 that “In general,
neither is learning the same as teaching, nor is effecting change the
same strictly speaking as undergoing change, but that to which they
belong—the motion—is.”

13.Physics 5.2, 225b11–13. The claim, then, can be
reformulated so that in all cases where there is a change in relation,
some non-relational change has to take place in some of the entities
which stand in relation to each other, hence there cannot be a
strictly and exclusively relational component which solely by changing
in and of itself would bring about relational change. Note that this
thesis about relational change leaves relation as a category in a
peculiar position: it turns out to be a dependent but ineliminable
type of entity. It is dependent, as any predication in the category of
relation presupposes corresponding predications in non-relational
categories, but it nevertheless remains ineliminable: any analysis of
a relation needs to mention alongside the more fundamental categorical
items some relational entity as well.

14.Physics 5.2 asserts at 225b13–16 that there is no
motion of the agent and of the passive counterpart. The enumeration in
the second half of this sentence—“neither is there motion
of the moved and of the mover, because there is no motion of motion,
or generation of generation, or change of change” shows that
motions are linked to actions and passions in an intimate way. (Note,
however, that for all this intricate connection, and the fact that
Aristotle reformulates his account at the end of Physics 3.3,
at 202b26–27 with the words “Furthermore, [in a way
through which it will be] more known
(gnôrimôteron) it [motion] is [the actuality] of
what is active in capacity, and of what is passive [in capacity] as
such”, Aristotle will still need to argue in books 7 and 8 that
the same item cannot house both the active and the passive capacity
for the same motion.

15.
Note that this argumentation does not address the category of time as
a domain of change. This is so either because the list of relevant
categories did not contain time in the first place, or because even
though it was present at that point, claims for its housing change
were dropped without explicit argumentation. Either way, this would
mean that time has been tacitly discarded from the list of relevant
categories at some stage by Aristotle. One obvious consideration could
be the fact that time is involved in all the possible forms
of motion (see e.g. Physics 5.4, 227b24–26 or 8.8,
262a2–5), but differences in time that would be present in every
instance of motion and rest do not constitute a specific form of
motion, the putative motion in time.

16.
Alternatively, one could claim that the restriction that motion is
the actuality of the potential in so far as it is potential
may characterise the potentials for motion that are present only
during the motion (cf. Charles 2015, p. 192). Potentials for the
end-state may be different in that they may remain even when the
end-state is already in actuality. This latter suggestion, however,
will be in conflict with Aristotle’s claim in this context
(discussed in the next paragraph) that the same item cannot be both
potentially and actually hot at the same time and in the same respect.
Accordingly, something can be heated during the same period when it is
potentially hot, and will lose both capacities—the capacity to
be heated and the capacity to be hot—when it is already hot in
actuality.

17.
Nevertheless, by selecting between different types of actualisations,
the restriction excludes some potentialities which do not have
actualities in so far as they are potential. Metaphysics 9.6,
1048b18–35 contrasts (incomplete) motions and (complete)
activities (praxeis), and asserts that the latter are
realised in a non-processual manner. Potentialities corresponding to
this latter type of actuality, then, cannot be actualised in so far as
they are potential, they have only complete actualisations (See
Burnyeat, 2008.)

18.
See Physics 3.2, 201a11–15, where he lists as
different kinds of motion the actuality “of the qualitatively
changeable in so far as it is qualitatively changeable, is qualitative
change, of that which is capable of growth, and of its opposite, of
that which is capable of decay, is growth and decay, of that which is
capable of coming-to-be and perishing, is coming-to-be and perishing,
and of that which is capable of locomotion is locomotion.” This
leads at Physics 3.2, 201a27–29 to Aristotle's
elucidation of the definition of motion, where the actuality of a
potential being in so far as it is itself (hêi auto) is
contrasted to its actuality in so far as it is capable of undergoing
motion (hêi kinêton).

19.
Cf. the concept of possible (endechomenon, occasionally also
dunaton) Aristotle commonly uses in his modal logic in the
Prior Analytics. What is necessary, as Aristotle stresses
there, can be said to be possible only in an equivocal sense
(Prior Analytics 1.13, 32a18–21, cf. 1.3,
25a37–39). This means that in its canonical use the possible
excludes necessity, although it does not exclude that the possible
state of affairs is in fact the case (that the predicate
holds—huparchei—of the subject of the
proposition). Accordingly, use of an (as it were mere)
potentiality (dunamis) in the definition of motion, which
disappears once the corresponding property is actualised, should be
viewed as introducing a further restriction along the same lines as
the stipulations in the Prior Analytics about the possible.
(Note, furthermore, that the claim would be trivially true if
Aristotle had not spoken here about capacities for being in some
particular state, but had referred to the special capacities for
undergoing change, and not the ones for possessing attributes which
characterize a state, reached as the end result of a change. After the
completion of a change the capacity to undergo that very change will
not be present any longer: once someone has reached Athens she no
longer possesses the capacity to get there. That capacity can only be
regained, upon leaving that location.)

20.
Although this threefold scheme has obvious links to the hylomorphic
analysis of entities into their matter and form, it need not be
identical with it for two main reasons. (1) What is identified in
processes other than generation as form is not the form of the entity
in the terms of a hylomorphic analysis, but a property of this entity.
(2) Even in cases of generation, where the form acquired is the form
of the entity, what Aristotle specifies as the substrate of the
generation need not be the matter of the emerging entity: the matter
of the entity can be coordinate with the form to the extent that that
matter is also generated from the preexistent material during the
process of generation. E.g. the material component in the generation
of plants is the seed, but this and the additional nutrient is
processed in the course of generation completely into the tissues
forming the organs of the emerging plant. In a hylomorphic analysis
the matter of the emerging plant is these tissues and organs, but they
cannot precede the living organism, since they cannot exist outside
the plant.

21.
Cf., further, the definition of effecting motion, which cannot avoid
referring to the entity being moved: “for the actuality in
relation to it [to the movable entity], in so far as it is such [i.e.
movable] is the same as effecting motion” (Physics 3.2
202a5–6).

22.
This consequence can be mitigated by a mapping of physiological
states onto psychological ones. In this case a physical property of
the sleeping pill will produce a similar physical property in the body
of the patient taking the pill, and the process then will be
redescribable by the mapping of physiological to psychological states
as a process causing the psychological state.

23.
Note that Aristotle repeatedly contends that Plato's Forms are
causally idle. Moreover a Platonic Form—e.g., knowledge itself,
or motion—is, as Aristotle puts it, at most a potentiality when
compared to a substance exercising the corresponding
potentiality—e.g. a knowing thing, or a thing in motion
(Metaphysics 9.8, 1050b34–1051a2).

24.
In the case of the generation of elements, Aristotle describes their
generator as “that which produces weight,” or “that
which produces lightness”. (baruntikon and
kouphistikon, see De caelo 4.3, 310a32). But
elements are also exhaustively characterised by the pair of elemental
properties hot-cold and dry-moist, and these are also causally
operative in processes of assimilation, when an elemental mass
transforms another element in its vicinity.

26.
Cf., furthermore, the case of perception, which is described in terms
of an external causally efficacious agent, the object of perception,
and as an internal switch from first to second actuality. The fact
that perception is accounted for through the combination of these two
different explanatory frameworks can be meant to capture its
intentional nature, its inherent activity, even though it is a passive
process, receptive of the form of the object of perception.

27.
For the fundamental difference between locomotion and the other
changes see Physics 8.7, 261a19–23 (cf. furthermore
Metaphysics 9.8, 1050b19–30).

28.
Note, furthermore, that when in De generatione et
corruptione 1.5 Aristotle gives a more thorough description of
what happens in quantitative change, the process is not described in
terms of the operation of a synonymous cause: it is not large objects
which confer a large extension on an entity that was initially small.
Quantitative change remains describable in terms of assimilation (or
discrimination) of entities, but these processes will be substantial
changes as far as the assimilated or dissimilated and segregated
entities in the process are concerned (see esp. De generatione et
corruptione 1.5, 322a11–13, where the causally efficacious
entity in the growth of flesh is located in the growing entity itself,
and it produces flesh in actuality out of the nutriment, which is
flesh in potentiality).

29.
Cf. Metaphysics 12.3, 1070a4-5, announcing the principle of
synonymy about substantial items only, and De generatione et
corruptione 1.5, 320b17–21, where the principle of causal
synonymy is relaxed to the almost non-committal requirement that in
some cases it is an entity in actuality of the same sort or of the
same kind as the effect which is causally efficacious, whereas in
other cases the cause is an actuality, but not an entity of the same
kind as the effect. Aristotle's example for the latter is the process
effecting rigidity: this does not require a cause which would be rigid
in actuality. (Cf. Rashed’s note in his edition of De
generatione et corruptione, pp. 123–124. Note, furthermore,
that the example is removed from the text by Joachim. The text without
the example, then, can also be understood as introducing a distinction
of causal types—one, entities of the same kind as their effects,
the other the causally salient factors or characteristics of such
causes, e.g. their forms. These are not the same kind of entities as
their effects, but they are actualities nevertheless, so Alan Code in
de Haas – Mansfeld, 2004, p. 178.)

30.
Moreover, another cluster of cases where form is
transmitted—the transmission of sensible form through the medium
in the process of perception—may also conform to this pattern.
Color effects a change in (“moves”) the transparent
medium, and in turn the medium effects a change in the sense-organ. As
a result of this process the form of the object of sensation (without
its matter) is transmitted to the sense. Note, however, that this
account does not necessarily require that the perceptible form needs
to be present in the medium in the same way as it is present in the
object of sense or in the sense-organ (the relationship between these
latter two modes of the existence of the perceptible form is a further
issue of contention, see Section 6 (Perception) of the entry on
Aristotle: Psychology).

31.
Aristotle can refer to the causally operative form in the mind of the
craftsman as identical to the form of the emerging artificial object,
but this is clearly a partial description only (Metaphysics
7.7, 1032b11–14, Metaphysics 12.4, 1070b33 and
Metaphysics 12.10, 1075b10): the form of the object in the
craftsman's mind is not just a blueprint. This is the craft itself,
which in its different applications can be operative in the
construction of different buildings, or in the treatment of different
ailments of different patients. Hence it needs to include all the
relevant information of the rules of the trade how to effect this
particular form in the matter. (For the difference of the cause and of
the effect in artificial change see Physics 2.7,
193b12–17.)

32.
As a rule, this contact is mutual, and hence the causal interaction
goes both ways: the entity effecting change is in its turn exposed to
the influence of the moved entity, it is being moved by it, albeit in
another respect (Physics 3.2, 202a5–9). This
requirement of mutual contact between mover and moved holds for most
cases of locomotion, hence the need for the complicated machinery in
the explanation of projectile motion in Physics 8.10. It can
be relaxed in two ways: either by the introduction of intermediaries
(the medium in the case of perception, the pockets of air propelling
the projectile on when it is no longer in contact with the original
source of motion, and the tools in the hands of the craftsman), or it
can even be downgraded into a one-directional contact, as the one
between the unmoved movers and the objects moved by them.

33.
Generation involves the other kinds of change according to
Metaphysics 9.1, 1042b3–5. Aristotle stresses
(Physics 8.7, 260b30–261a7) that these considerations
are not refuted by the fact that in the individual history of each
entity generation necessarily precedes any locomotion performed by the
entity, or furthermore by the fact that living beings undergo
qualitative and quantitative changes before they could possess their
specific form of locomotion. What comes in the individual history last
can be the most fundamental form of change, similarly to the claim
that the fully developed living being in actuality is causally prior
to all the imperfect stages in the actual generation of the member of
a species (see Peramatzis, 2011).

34.
For this Aristotle relies on a principle of modal plenitude: whatever
is always possible, needs to be actualised at one point of the history
of the world. (See also the article
Aristotle: Logic.)
This principle is discussed in detail in De caelo 1.12, at
the end of a book arguing for the thesis that the eternal heavens need
to be composed of a special celestial stuff, which is exempt from
coming to be, perishing or change, and performs the celestial
revolutions as its natural motion. See further Metaphysics
9.4.

35.
For the discussion of the introduction of unmoved movers see the next
Section. In Metaphysics 12.8, Aristotle opts for both the
uniqueness and the plurality of the unmoved celestial movers. Each
celestial sphere possesses the unmoved mover of its
own—presumably as the object of its striving, see
Metaphysics 12.6—whereas the mover of the outermost
celestial sphere, which carries with its diurnal rotation the fixed
stars, being the first of the series of unmoved movers also guarantees
the unity and uniqueness of the universe.

36.
The serial infinity in the case of humans is asserted at
Physics 3.6, 206a25–27, alongside with the serial
infinity of time or of successive divisions of magnitudes.

37.De caelo 2.7, 289a19–35, and recall the special case
of the physician's rub causing heat in the body of the patient in
Metaphysics 7.9, which, accordingly, turns out to be
analogous to the most fundamental interaction between the celestial
and the sublunary domains.

38.
See Metaphysics 12.5, 1071a14–17, where Aristotle also
mentions that these latter moving causes are not instances of the same
form as their effects, i.e. the principle of causal synonymy does not
hold in their case. For an almost cryptically shorthand form of the
same example see Physics 2.2, 194b13.

39.
Commentators of late antiquity will assert that the uppermost
sublunary region, composed of a material analogous to fire, hence
already at its natural place, performs its circular motion under the
influence of the celestial spheres neither by force nor according to
its nature, and they label such motions as ones superadded to nature
(huper phusin). Note, moreover, that Aristotle's account of
heavenly motions also requires a class of locomotions of such an
intermediate status, because he holds both that there is no forced
motion in the celestial domain, and at the same time that planetary
motions are the result of the composition of the rotations of several
different spheres, each of these spheres performing a component of
these motions as its own, whereas the other component is as it were
superadded to it (De caelo 2.12, 293a9–11, cf.
Metaphysics 12.6, 1072a10–18).

40.
Note that even without the principle that natural and forced motions
come in pairs of opposites Aristotle could establish the existence of
an eternal celestial element, which performs the eternal heavenly
revolutions as its natural motions (De caelo 1.2,
269b2–12, and see 1.3, 270b11–16 and b4–11). Such an
eternal element would be removed from the sublunary processes of
changes, and by a principle of modal plenitude announced in De
caelo 1.12 it can be established that this element is
necessarily ungenerated and imperishable.

41.
The centrality of what is natural can be further underlined by
Aristotle’s remark that even deviations from the natural course of
events—say, the generation of monstrosities—also have
natural causes, or as On the generation of animals 4.4,
770b15 puts it “even what is contrary to nature is in some way
according to nature” (cf. Descartes’ considerations about
“defective natures” in his Sixth Meditation, pp.
84f Adam-Tannery).

42.
This means that in the case of every motion both the actuality of the
moved entity and the actuality of the mover are present in
the moving object, cf.
note 14
above.

43.
This translation rests on the reading of the manuscripts: the element
is by its very nature towards some place (pephuken poi).
Simplicius reads pephuken pou—“is by its very
nature somewhere.”

44.
See the previous Section for the exposition what the finitude of
these causal chains amounts to, and how it is compatible with the
existence of infinite causal chains.

45.
Why unmoved? Causal chains can terminate in unmoved movers or in
self-movers. If the celestial spheres are not self-movers, they might
still be moved by moved movers. But then at an ultimate remove their
movers will have to be self-movers, or be moved by unmoved movers,
otherwise the cosmos will depend on an infinite chain of causes.

Indeed, after giving specific figures for the number of celestial
movements, Aristotle argues at Metaphysics 12.8,
1074a17–31 that the number of spheres, and the number of
celestial unmoved movers necessarily has to be the same as the number
of component movements of the motion of the stars (see Judson, 2015,
pp. 179–187 and Bodnár 2016, pp. 262–266).

46.
Accordingly, Physics 8.6, 259b20–24 asserts that the
prime mover has to be unmoved both in itself and also accidentally,
contrasting it thereby to the souls of sublunary living beings. Even
though these souls are unmoved movers, nevertheless they move
themselves in an accidental manner through the motion they induce in
the living body.

47.
The word used here for power is dunamis, but as the unmoved
mover is nothing but actuality it cannot refer to an intrinsic
infinite potentiality of the mover. This infinite power or
capacity is attributable to this entity specifically—and
exclusively—in relation to the object moved. Nevertheless, this
does not compromise the status of this entity as being fully and
unqualifiedly actual.

48.
Or otherwise put: in standard cases the mover’s actuality is
matched by the passive potentiality of the moved entity for the same
kind of actuality. This kind of intimate connection is not present in
the case of the activity of the prime mover—which is a
completely intellectual activity—and the activity induced in the
celestial spheres. (See Bordt 2011.)

49.
Note the way Theophrastus Metaphysics 8–9,
5a28–5b10 uses the fact that the mover of the celestial
revolutions is an object of striving as a basis for a clear
distinction between the transcendental mover and the souls of the
celestial bodies, which strive after this entity.